Given this vacuum, attention has recently turned to some excellent nongovernmental attempts to compile this data, including the Fatal Encounters database, the recently created Gun Violence Archive and a new database created by Deadspin.

But one recent effort stood out for its apparent comprehensiveness: The Killed By Police Facebook page, which aggregates links to news articles on police-related killings and keeps a running tally on the number of victims. The creator of the page does not seek to determine whether police killings are justifiable; each post “merely documents the occurrence of a death.” He told FiveThirtyEight that he was an instructor on nonviolent physical-intervention techniques and that he prefers to remain anonymous.

Killed by Police had listed more than 1,450 deaths caused by law-enforcement officers since its launch, on May 1, 2013, through Sunday. That works out to about three per day, or 1,100 a year.

The page doesn’t claim that this is a comprehensive count, but it could be useful — like the count from the FBI’s annual Supplementary Homicide Report is useful — for setting a baseline number of police killings, as long as important caveats are acknowledged. For one, any database drawn from news sitesrelies on the assumption that the reports are accurate. If there is follow-up reporting that changes the initial understanding of the killing (for example, if it was later determined that a suspect committed suicide during a shoot-out with police), that follow-up wouldn’t necessarily be reflected in the Killed By Police tally. Finally — and most important — we can’t trust the Killed By Police numbers without checking the links.

We randomly sampled 146 incidents (10 percent) from the news links posted to Killed By Police. All the posts linked to established outlets, although in some cases a new url for the article had to be found because the news site had restructured its links. Here’s a breakdown of these incidents:

124 incidents (85 percent) were clear-cut police shootings in which the victims were fatally shot by officers acting in the line of duty. “Line of duty” doesn’t necessarily mean “justifiable,” but it’s an important distinction because it excludes some incidents, such as one in which an off-duty officer shot and killed a friend during a bar fight and was subsequently charged with criminal homicide. This count does include a few cases of off-duty officers using deadly force while acting in a law-enforcement capacity.

12 incidents (8 percent) were other cases of arrest-related deaths in which the victims died after being Tasered or otherwise restrained by law enforcement officers. These incidents are more complicated than shootings; the exact cause of death is harder to pin down. In some cases, a victim’s preexisting health issues are blamed.

10 incidents (7 percent) were killings by police officers acting outside the line of duty or accidental deaths. Examples include an officer who killed two women in a drunken-driving accident, a murder-suicide in which an officer killed his ex-wife, and a woman killed in a collision with a police SUV that was pursuing a suspect. These are all newsworthy deaths, but they aren’t examples of the use of deadly force by police officers in the line of duty. We wouldn’t necessarily expect a comprehensive governmental database of police killings to include them.

By the narrowest measure possible — in which we give police every benefit of the “cause of death” doubt in incidents where they Tasered or restrained suspects – 85 percent of the sampled incidents were the sort of police killings the government might be expected to keep track of. If we include other arrest-related deaths (and they’re included in Bureau of Justice figures), then 93 percent of incidents qualified as police killings.

Applying these percentages to the total count at Killed By Police would imply that officers acting in the line of duty have killed in the neighborhood of 1,250 to 1,350 people since May 1, 2013. That’s about 1,000 deaths per year.

This estimate isn’t directly comparable to the FBI’s “400 police homicides” count, because that figure is only available through 2012, and the previously mentioned caveats about media-report-driven counts apply.

Nevertheless, it’s a good indication that “400 police homicides” isn’t a useful baseline number for the number of people killed by police each year.

Note: Not all posts are visible on the Killed By Police page because of a Facebook algorithm, but we were able to scrape them. Every link can be found in this spreadsheet.

Reuben Fischer-Baum is a visual journalist for FiveThirtyEight. @reubenfb

Al Johri is the computational journalist intern for FiveThirtyEight. @aljohri